In a previously known rock drill rig, the rock drilling machine is fastened to a slide being movable to and fro on a feed beam. The transfer of movement from a drive motor to the slide is over a chain transmission which is fastened to the slide.
Because of wear, the drive chain will experience a successive elongation during operation which is the reason for proposals of different arrangements for tensioning the drive chain. Hereby pressing means are previously known that press laterally against a part of the chain with a certain force in order to absorb slack in the drive chain. Another previously known chain tensioning mechanism is comprised of a displacement device for a wheel being arranged in the chain transmission.